Free or open source databases run hundreds of millions of public-facing and private applications worldwide, but how effective is this technology and how do these products compare? For answers, we reviewed six popular free or open source database products: Microsoft SQL Server Express, PostgreSQL, Oracle's MySQL, MariaDB, Apache Derby and Firebird SQL.

When selecting candidates for our review we chose fully featured relational database management system (RDBMS) products with features such as procedures, functions, triggers and cursors. While we did not set out to perform scientific benchmarking, we did test large tables. For the test data, we used a truncated log file from one of our Web servers containing a million-plus records. The same test data was used across all six products. We ran standard tests such as bulk inserts/imports and performed data manipulation tasks via SELECT, UPDATE AND DELETE statements.